Relation between athletic club affiliation from school age and future serum free testosterone levels in Japan: A cross‐sectional study

Abstract Background and Aims Testosterone deficiency is often related to geriatric syndrome including erectile dysfunction, osteo‐porosis, depression, cognitive impairment, cardiovascular diseases and frailty. Despite the existence of many studies on short‐term exercise and serum testosterone levels, few research have focused on exercise habits from young age and testosterone values in middle‐aged male. In this study, we investigated whether belonging to an athletic club from school age could predict serum‐free testosterone (FT) levels. Methods The subjects were 1609 middle‐aged male outpatients aged 40 years or older (median: 61 years, interquartile range: 54–69) who visited our hospital. Participants had their FT values measured in the morning hours during the period from December 2007 to June 2009. A questionnaire survey on exercise habits was conducted at the same time as the measurements. The exercise habit questionnaire was created based on whether the patients belonged to an athletic club in (a) elementary school, (b) junior high school, (c) high school, (d) college, (e) adult life, and (f) at the time of the test. Results There was only one positive response to the questionnaire among 456 patients (28% of total), followed by zero for 358 patients (22% of total). The number of patients with low‐testosterone levels (FT < 8.5 pg/mL) according to the Japanese diagnostic criteria for late‐onset of hypogonadism was 839 (52.1%). In multivariate analysis, it was shown that with low‐testosterone levels (FT < 8.5 pg/mL), age (odds ratio [OR]: 1.065, 95% confidence interval [CI]: 1.052–1.079; p < 0.001), hypertension (OR: 3.489, 95% CI: 2.728–4.462; p < 0.001), type‐2 diabetes (OR: 3.035, 95% CI: 2.296–4.01; p < 0.001), and dyslipidemia (OR: 2.039, 95% CI: 1.558–2.668; p < 0.001) were risk factors, and more than two positive responses to the questionnaire (OR: 0.886, 95% CI: 0.802–0.980; p = 0.018) were also a significant independent factor. Conclusion A sports club membership during school years may affect future testosterone levels.


| Study population
From 2007 to 2009, 1682 male subjects aged more than 40 years with metabolic factors, comprising, dyslipidemia, hypertension, and type-2 DM, inspected serum FT value at our outpatient clinic for the testing late-onset hypogonadism (LOH) syndrome. At the first visit, blood was collected between 09:00 and 11:00 to determine serum FT values employing radioimmunoassay (DPC Free Testosterone Kit, Mitsubishi Kagaku Iatron). All 1682 of these patients were included as inclusion criteria for our study. The diagnosis of hypogonadism was based on the Japanese criteria for FT levels ≤8.5 pg/mL. 15 Dyslipidemia, type-2 DM, and hypertension were diagnosed in compliance with the Japanese diagnostic criteria or medical treatment with any agent for such diseases. 16,17 A total of 73 patients who did not fill the questionnaire were eliminated. No further inclusion and exclusion criteria were established to analyze real data from actual clinical practice. Among the 1682 patients, 1609 were eligible for the analysis.

| Questionnaire on exercise habits from school age
The participants were surveyed about exercise habits from school age based on a questionnaire that was completed before the physical

| Data analysis
First, the FT levels per response to the exercise habits questionnaire were compared by analysis of variance (ANOVA) test. The collected data were divided into two groups according to serum FT levels (≤8.5 pg/mL or >8.5 pg/mL). They were then compared in univariate analysis. Chi-squared test and the Mann-Whitney U-test were applied to decide the factors related to hypogonadism. The multivariate logistic regression model was made on the ground of the same covariates in the univariate analysis. The statistical analyses were conducted using SPSS™ statistics (version 22, SPSS Inc.). In all analyses, p-values of <0.05 were considered statistically significant using a two-tailed test.

| RESULTS
In our study (1609 participants), the median of age and serum FT level were 61 (interquartile range [IQR]: 54-69) and 8.3 pg/mL (6.4-10.3), respectively (Table 1). No significant differences were found in FT levels per response to the questionnaire on exercise habits (Table 2).
The baseline characteristics of the patients on the basis of FT levels are summarizing in Table 3. Participants with hypogonadism who were significantly older were associated with fewer positive questionnaire responses and indicated a higher frequency of developing hypertension, dyslipidemia, and type-2 diabetes compared with those without hypogonadism. No significant difference in BMI was observed between the two groups ( Table 3).
The results of the questionnaire are displayed in Figures 1 and 2.
There was only one positive response to the questionnaire among 456 patients (28% of total), followed by zero for 358 patients (22% of total) (Figure 1). Those who answered that they were currently in an athletic club (211/1609) were those who most likely had three positive questionnaire responses, which corresponded to 23% (49/ 211), followed by 20% (43/211) for those who provided four positive responses, and 64% (136/211) for those who provided three or more positive responses ( Figure 2 (Table 4). In addition, two or more positive questionnaire responses constituted a significantly independent factor for non-hypogonadal states (OR = 0.886; 95% CI = 0.802-0.98; p = 0.018).

| DISCUSSION
This study suggested that belonging to athletic clubs during many periods from school age to the present is related to hypogonadism states in middle-aged Japanese patients diagnosed later in their lives.
This was the largest research in the literature that demonstrated that athletic affiliation exercise habits constitute an independent factor for the LOH syndrome within the Japanese population. Sixty-four percent (135/211) of those who answered that they were currently in an athletic club provided three or more positive ("yes") questionnaire responses ( Figure 2). This indicates that the majority of those who currently belong to an athletic club have been members of a sports club since their school days, thus suggesting that they have continued the habits of exercising since childhood. In this study, provision of two or more positive questionnaire responses of the questionnaire was a significant and independent factor for avoiding hypogonadal states in multivariate analysis. Implementing exercise habits from childhood or adolescence is considered to be related to high-testosterone levels independently of diabetes, age, and hypertension. The results of each of the exercise habits questions showed no significant differences in testosterone levels for either "yes" or "no" answers ( Table 2). This also could support the aforementioned conclusions.
Several research studies that have focused on short-term exercise and testosterone have been reported. 14,18 They have suggested that regular 12-and 6-week acute aerobic exercise increases circulating levels of testosterone in healthy young and older men. These previous studies have implied that bouts of aerobic exercise, particularly high-intensity aerobic exercise, increase serum testosterone levels in men. However, it could not be ruled out that high-intensity exercise only temporarily increases testosterone levels.
None of the trials were able to evaluate the association between exercise habits and long-term testosterone levels. This study discusses the association between exercise routine from childhood, which we believe is noteworthy because (to our knowledge) few relevant reports have been published.
Not only high-intensity exercise but also low-intensity sport could make a positive impact on the development in testosterone. 19 T A B L E 1 Patient background information.  modes of exercise could lead to an elevation of cortisol and testosterone, thus maximizing the beneficial effects on growth and development, when exercise is performed in the evening hours. 23 In terms of childhood and evening exercise, belonging to a school-age sports club is just perfect. Our study supports these research.
BMI and waist circumference were negatively correlated with testosterone levels, although BMI was not associated with low testosterone levels in this study. 24 Some Japanese studies have found no association between BMI and low-testosterone, similar to this study. 9 The prevalence of obesity and overweight in Japanese adults is rather low in international comparisons 25 and could explain why BMI was not a significant factor in this study.
This study is associated with some limitations that are worth noting. First of all, this questionnaire was filled in by the patients themselves, and therefore the reliability of the results could not be guaranteed. Second, the patients only confirmed their affiliations with athletic clubs from their school days, and the types of daily physical activities were unclear owing to the many types of athletic clubs. The "exercise habit questionnaire" in this study just examined whether and when the participants were athletic club members. The participants belonging to an athletic club may not directly indicate participants' "exercise habits" or "exercise routine" during young age.
The amount of time spent in physical activity during their school years is also unknown. Kawaguchi et al. examined the association between group physical activity and exercise adherence among elderly community-dwelling individuals who participated a community exercise club. 26 The results showed that group program participants tended to participate in the exercise program more continuously than non-participants (Prevalence ratio = 3.63; 95% CI: 1.98-6.65, p < 0.01). There was also a significant positive correlation between group program participation and exercise adherence for physical activity is more likely to be sustained in a group setting for elderly members as well as young adolescents than alone. 27 The activities in an athletic club are group program itself, and these findings propose that belonging to an athletic club could be highly related to exercise habits. However, it does not directly reflect or be related to the actual "exercise habits" or "group exercise habits" in the past or now as well. Even in the recent study, there is an insufficiency of evidence/logic/references to confirm the claim that athletic club affiliation is related to different kinds of physical activity levels, exercise types, or habits. Therefore, it is considerable to refer to the conclusion of the current study that "athletic club affiliation is related to future serum FT levels" does not necessarily indicate that exercise habits from school age are associated with future testosterone.
We believe that a large and long-term prospective cohort study is needed to determine what type of intensity of exercise (implemented from a young age) has a long-term effect on future testosterone levels.
In addition, the examination of serum FT values using radioimmunoassay is generally unreliable according to the guidelines from the European Academy of Andrology, 3

the American Urological
Association. 28  On the other hand, testosterone measurements necessitate twice performance on separate days, 3 but only single FT measurements was conducted at baseline in our study. In addition, testosterone levels in seminal plasma have recently been reported to reflect spermatogenesis in the testis. 31 However, the relationship and differences between serum and seminal plasma testosterone values are unknown and little study has been conducted. It is also difficult to refer to the significance of seminal plasma testosterone measurements because it is unclear whether low plasma testosterone represents the same pathogenesis as testosterone deficiency that has been reported so far. 3 Therefore, we believe that prospective studies on the association between exercise habits and future serum testosterone levels as well as plasma testosterone levels should be worthy of consideration.
Finally, there are many confounding factors in the studies about testosterone level that may affect their assessments and evaluation of the subjects (e.g., duration of marriage, sexual behavior, multiple